Wrench and spanner name the same tool for gripping and turning nuts and bolts: wrench is the American term, spanner the British one. Wrench also has extra jobs as a word, covering a sudden painful twist and the verb for wrenching something open.
The core difference
The two words label the same hand tool, but wrench is American English and spanner is British English.
- wrench — US term for the tool used to grip and turn nuts, bolts or pipes: He grabbed a wrench from the toolbox to tighten the bolt.
- spanner — the British word for the same tool, and also a problem thrown into the works: The delayed shipment threw a spanner in the works for the launch.
- wrench — also a sudden, often emotional, twist or pull, or the verb for twisting something violently: She wrenched the door open before it could lock again.
How to tell them apart
If you are reading American English, reach for wrench; if you are reading British English, reach for spanner. Both describe the identical tool, so there is no difference in the object itself, only in which side of the Atlantic named it. Spanner comes from "span" plus "-er", literally a thing that spans or grips something, while wrench traces back through Old English wrenċ to a Proto-Indo-European root meaning "to turn".
Wrench carries a second life beyond the toolbox. It describes a sudden, often painful twist, as in an emotional wrench of separation, and it works as a verb for pulling or twisting something suddenly, such as wrenching a knee. Spanner keeps its extra sense too, in the phrase "a spanner in the works", meaning an unexpected obstacle.
